Mycotoxins

Question 1

Ex of Mycotoxins

Answer 1

Ergotism

Aflatoxins

Question 2

What is Ergotism

Answer 2

Associated with contaminated grains – particularly Rye

Caused by the fungus Claviceps purpurea

Under cool damp conditions the fungus invades grain kernels – produces sclerotia

Question 3

Ergotism are ?

Can be classed as what family (& Ex)

Answer 3

Toxins are alkaloids

Ergot family: Ergotamine & Ergocristine
Clavine family: Agroclavine , Elymoclavine & Lysergol
Lysergic acid diethylamide (LSD)

Question 4

2 types of Ergotism

Answer 4

Gangrenous ergotism

Convulsive ergotism

Question 5

What is Gangrenous ergotism

Answer 5

Severe pain and inflammation of the extremities
Become blackened - can lead to loss of fingers and toes
Caused by the ergot family alkaloids

Question 6

Gangrenous ergotism mechanism

Answer 6

ergot family alkaloids has Structure similar to neurotransmitters [ Dopamine / Serotonin / Adrenaline] – bind to receptors and interfere with signal transduction pathways

Ergotamine binds more strongly and dissociates more slowly

Question 7

What is Convulsive ergotism

Answer 7

Caused by the clavine family alkaloids

induce Neurological symptoms
Writhing, tremors, numbness, blindness, convulsions, hallucinations and psychosis

Question 8

Convulsive ergotism mechanisms

Answer 8

Physiological mechanisms are poorly understood

Likely to bind to dopamine and adrenoreceptors

Question 9

Brief history of ergotism

Answer 9

In 1692 in Salem Massachusetts, Betty Parris, Ann Putnam, Mercy Lewis and Mary Walcott experienced hallucinations, convulsions and erratic behaviour
….. Almost certainly convulsive ergotism

Puritans in Salem blamed witchcraft…
Over 100 people arrested and 20 killed in subsequent witch hunt – at least 4 more died in prison

Question 10

Aflatoxins Originally identified as a problem in ___?

Caused by _____?

Answer 10

in animal feed “Hepatitis-X”
–> causing Liver necrosis and liver cancers in dogs, swine, cattle

Caused by feed contaminated with fungi: Aspergillus flavus & Aspergillus parasiticus

Question 11

When Aflatoxins was identified as a human health concern ?

Answer 11

identified as a human health concern in 1960

Question 12

Acute toxicity of Aflatoxins

Answer 12

Large species variation seen with toxicity: [ LD50 (mg/kg body weight)]

Male rat = <2.0
Female rat = 18
Mouse = >9
Non-human primates = 2.2.- 8.0

Question 13

Health effects of Aflatoxins

Answer 13

Causes liver necrosis, hepatic lesions and oedema

Question 14

Mechanism of Aflatoxins

Answer 14

B1/ B2 / B2a give Blue fluorescence (with a 5 carbon ring - CH2)
G1/ G2 / G2a give Green fluorescence (with a 6 carbon ring - O)

B1 & G1 which have a Unsaturated furan ring is much more toxic

Convert B1 –> B2a & G1 –> G2a
Saturating the unsaturated furan ring with an alcohol group

Question 15

what is AFB1 ?

Health effects?

Answer 15

an aflatoxin that is a potent liver carcinogen in animals and humans

Effect on hepatic cancer incidence is unclear however
Carcinogenity is enhanced if Hepatitis-B infection is present:
Hepatitis-B virus acts as a tumour-promoter – results in 15-fold increase in cancer risk

AFB1 can also cause lung cancer in humans on inhalation

Can occur with contaminated grain dust

Question 16

Aflatoxins can be found in

Answer 16

Rice / barley / rye /corns
Peanuts / soy beans / wheat / Sweet potato
Sorghum

Question 17

Risk of Aflatoxins increased by

Answer 17

Problem arises when produce is stored under low moisture conditions

Question 18

Aflatoxins can inhibit _____?

Answer 18

Inhibit growth of Penicillium and Fusarium fungi – compete with Aspergillus flavus

Question 19

How to prevent Aflatoxins

Answer 19

Cannot realistically be prevented from contaminating food supply
Need to decontaminate suspect food
Contamination can be detected by fluorescence:

However, A. flavus also produces kojic acid which is non-toxic but is also fluorescent – need chemical analysis to confirm

Question 20

Regulatory bodies set allowable limits of aflatoxins

Answer 20

US FDA Foods (ppb) = 20 Milk (ppb) = 0.5

EU EFSA Foods (ppb) = 4 Milk (ppb) = 0.05 [0.025 ppb in milk-based infant formula food]

Question 21

How to stable or reduce Aflatoxins

Mechanism ?

Answer 21

Aflatoxins are relatively stable to heat
Can be reduced by 80% in peanuts by roasting

Most common method is ammoniation – mild heating in liquid ammonia reduces AFB1 by 80%

slide 39